# MAL-2026-5579: Malicious code in webpack-cache-cycle (npm)


- **Type:** Malicious package
- **Package:** `webpack-cache-cycle` (npm)
- **Published:** 11 Jun 2026
- **Also known as:** GHSA-2p34-5qgm-wr3f

## What is MAL-2026-5579?

MAL-2026-5579 is a malicious package in webpack-cache-cycle, published on 11 Jun 2026. 

### Official description

On `npm install`, package.json's `postinstall` hook runs `node -e "require('./loader.js')"`. loader.js spawns a detached node process that decodes a hex-encoded URL (https://jsonkeeper.com/b/L435A — an anonymous, mutable paste host), performs an HTTPS GET, writes the response's `session` field to a temporary.js file, and `require()`s it — executing attacker-controlled JavaScript on the installer's machine. The URL is obfuscated as a hex literal padded with whitespace inside `Buffer.from(...)` to evade naive string scanners. The detached spawn lets `npm install` exit cleanly while the dropper continues asynchronously. The package's advertised purpose is a webpack cache plugin, which does not justify any network access at install time. The package name `webpack-cache-cycle` and README title `webpack-cache-plugin` impersonate legitimate webpack tooling, with placeholder author metadata (`Webpack Tools`) and a non-existent GitHub repository.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.

## What should I do about MAL-2026-5579?

Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.

## Fix prompt for AI coding agents

```text
MAL-2026-5579 is a malicious package: webpack-cache-cycle (npm). Every version was published to cause harm.

Task:
1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.
2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.
3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.
4. If the package is not used anywhere, say so and change nothing.

Reference: https://insights.sbomify.com/MAL-2026-5579/ (Markdown: https://insights.sbomify.com/MAL-2026-5579/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-5579

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-5579/
Summaries are generated and may contain mistakes; the official description above is the record.